1. Field of the Invention
This invention relates to a refrigeration working fluid composed of a halogenated hydrocarbon refrigerant having a high fluorine concentration and a branched chain alkylbenzene lubricant, said fluid being in a refrigeration apparatus of the sealed compressor type. In particular, the invention is concerned with such lubricants for use with such refrigerants in which the fluorine content is at least 40% by weight.
2. Prior Art
It has been known that difluoromonochloromethane, difluorodichloromethane, and methyl chloride are useful as refrigerating agents in refrigerating machines. It has also been known that difluoromonochloromethane and other high fluorine content halogenated hydrocarbons have certain essential advantages in comparison with the use of difluorodichloromethane which has been primarily used up to now. For example, difluoromonochloromethane has 1.6-1.7 times the volumetric refrigerating capacity as does difluorodichloromethane. Furthermore, in refrigerating machines operated with difluoromonochloromethane, lower cooling temperatures can be obtained in one-step operation than with difluorodichloromethane under otherwise equal conditions.
However, it is a disadvantage that in contrast to difluorodichloromethane the high fluorine content halogenated hydrocarbons are not completely miscible with the mineral oils conventionally used as lubricating agents at low temperatures. The consequence of this is that expensive oil separators and oil return devices must be built in refrigerating machines operated with these highly fluorinated hydrocarbons.
In order to overcome the above-mentioned disadvantages occurring in the use of fluorinated hydrocarbons, instead of mineral oils, secondary silicic acid butyl esters (silicones) have been used as lubricating agents. It has been found that such esters are well miscible with difluoromonochloromethane so that the use of oil separators and oil return devices could be dispensed with. However, the use of said esters has the disadvantage that they are relatively expensive and their lubricating effect is lower than that of mineral oils.
Another solution to the above-described miscibility problem is by the use of polyalkylated benzene as a lubricant; see U.S. Pat. Nos. 3,169,928 and 3,092,981. These polyalkylated benzenes are characterized as having at least two alkyl groups, a boiling point between 150.degree. and 330.degree. C. at 12 mm and a viscosity between 9.degree. E and 37.degree. E at 20.degree. C. and between 2.degree. E and 5.degree. E at 50.degree. C. The alkyl groups used are of both straight and branched chain structure. Those exemplified had from 10 to 13 carbons each.